TEXT PROCEDURE ROT13(INP); TEXT INP;
    BEGIN

        CHARACTER PROCEDURE ROT13CHAR(C); CHARACTER C;
            ROT13CHAR :=
                CHAR(
                    RANK(C) +
                       (IF C >= 'A' AND C <= 'M' THEN  13 ELSE
                        IF C >= 'a' AND C <= 'm' THEN  13 ELSE
                        IF C >= 'N' AND C <= 'Z' THEN -13 ELSE
                        IF C >= 'n' AND C <= 'z' THEN -13 ELSE 0));

        TEXT OUTP;
        OUTP :- BLANKS(INP.LENGTH);

        INP.SETPOS(1);
        WHILE INP.MORE DO
            OUTP.PUTCHAR(ROT13CHAR(INP.GETCHAR));

        ROT13 :- OUTP;
    END ROT13;